In an increasingly networked world, more and more traffic, such as data, voice, and video, is transmitted over public and proprietary networks. Wireless networks, in particular, are popular as networks through which subscribers obtain both voice services (e.g., telephone calls) and data services (e.g., email and web surfing).
Mobile devices, such as smart phones, that use wireless networks, can be limited by the battery life of the mobile device. Depending on how the mobile device is used, the time period before the mobile device needs to be recharged can be a day or less. Car charging and office charging of mobile devices are common.